Data Storage Devices (DSDs) are often used to record data onto or to reproduce data from a storage media. One type of storage media includes a rotating magnetic disk where a magnetic head of the DSD can read and write data in tracks on a surface of the disk.
A DSD may periodically perform garbage collection or defragmentation processes in order to make better use of space on the disk. In the case of garbage collection, the DSD attempts to free up space that is taken up by obsolete or invalid data. In the case of defragmentation, the DSD attempts to reorganize the locations of data on the disk to provide a more contiguous block of data.
Data objects that are frequently updated can create more obsolete or invalid data and greater discontinuities in where current versions of data (i.e., valid data) are stored. Garbage collection and defragmentation may therefore be performed more frequently for portions of the disk storing frequently updated data objects. Depending on the extent of garbage collection or defragmentation, such maintenance operations can consume significant resources of the DSD in terms of available memory and processing when copying and relocating large amounts of data on the disk.
Garbage collection and defragmentation can become particularly burdensome for portions of the disk utilizing Shingled Magnetic Recording (SMR). SMR has recently been introduced as a way of increasing the amount of data that can be stored in a given area on the disk by increasing the number of Tracks Per Inch (TPI) by overlapping tracks on the disk to result in narrow tracks at the non-overlapping portion of the tracks. Although SMR generally increases the recording density of the disk, SMR typically requires that the tracks are sequentially written since a new write to a previously overlapped track would also affect data in an adjacent track. SMR portions of a disk are therefore usually garbage collected or defragmented in their entirety. However, as noted above, frequently updated data objects can create a need for more garbage collection and defragmentation which can require additional resources for an SMR portion of the disk.